Telephone-exchange system.



L. H. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED MAY26,1916- Patented Jan. 16, 1917'.

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' ,Tlfi TA$ PATENT QFFTQEQ LEWIS H. JOHNSON, OF BLOOlvI-FIELD, NEW JERSEY, ASSIGNOR TO lVEETEBN ELECTRIC COMPANY, INCORPORATED, CF NEVI YOR K, N. "E, A CGRPGRATION 01 NEVJ YGRK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed May 26, 1916. Serial No. 99,977.

To all whom it may concern:

Be it known that I, LEW-1s H. JorrNsoN, a citizen of the United States, residing at Bloomfield, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-E20 change Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to such systems of the central energy type in which an operatoi s telephone set is automatically connected to and disconnected from a calling telephone line.

The object of this invention is the provision of means for increasing the effi ciency of the operators of a telephone exchange and for facilitating the completing at connections between subscribers.

In accordance with this invention, a telephone exchange system, in which the operators telephone set is automatically connected to a calling telephone line upon the connection of a link circuit therewith, is provided with circuits and apparatus, so organized that, while the operators telephone set is connected to one calling telephone line, it cannot be connected to any other calling line, but a second connection may be prepared during the existence of the first so that upon the disconnection of the operators telephone set from the first calling line, it will be immediately connected to the calling line forming a part of the prepared connection.

This invention is an improvement on that disclosed in the application of Henry P. Clausen, Ser. No. 59,972, filed November 6, 1915, in that less apparatus is required for accomplishing the desired result.

More specifically, this invention contemplates a telephone exchange system in which there are link circuits for interconnecting the lines and a difierentially wound relay associated with each link circuit for automatically connecting the operators telephone set with the talking strands thereof when connected with the calling telephone line, the operation of any one of the listening relays closing a break in the circuit with the neutralizing winding of each of the other listening relays in that position, so that upon the completion of the circuit through both the operating and neutralizing windings thereof, upon the connection of another link circuit with another calling line, the listening relay thereof will be prevented from operating.

This invention is illustrated in the accom panying drawing, in which there are shown ordinary subscribers lines A, B, C and D (lines 13, C and D being indicated merely by the answering jacks thereof), and cord circuits E and F for interconnecting the subscribers lines. The apparatus of each cord circuit is exactly alike, and-the same reference characters will be used to indicate the same apparatus.

Assuming that subscriber A wishes v to converse with subscriber B, A will signal the central oilice in the usual manner,

whereupon the operator will insert the answering plug of the cord circuit E into the jack associated with As line, causing the operation of sleeve relay 5 and supervisory relay 6. The operation of supervisory relay 6 causes the operation of listening relay 7 over a circuit from battery, through the upper winding of relay 7, alternate contact of supervisory relay 6 and supervisory lamp 8 to ground. Listening relay 7, in op erating, connects an operators telephone set 9 across the talking strands of the cord circuit E, and opens its contact 10 and closes contact 11. The closure of contact 11 connects battery to the common conductor 12, so that battery is now connected to one terminal of the lower winding of all other listening relays in that position through contacts 10, 10 of the listening relays and contacts 18, 13 of relays 14, 14. The operator, finding the desired number to be that of subscriber B, completes the connection by inserting the calling plug of cord circuit E into the jack associated with Bs line, causing the operation of relay 14, which opens its contact 13 and closes contacts 15 and 16. The closure of contact 15 connects battery to the lower winding of differential listening relay 7, which thereupon releases, opening its contact 11 and closing contact 10. The opening of contact 11 removes battery from the common conductor 12 and the lower windings of the listening relays in the other cord circuits of this position. The closure of contact 16 causes supervisory lamp 17 to light. The operator actuates ringing key 21 to send ringing current over Bs line to operate the call bell thereat. Subscriber B, in responding, removes the receiver from the switch-hook, causing the operation of supervisory relay 22 to efl'ace supervisory lamp 17. When the conversation is completed, both subscribers restore the receivers to the switchhooks, causing the lighting of supervisory lamps 8 and 17 to furnish disconnect signals, whereupon the operator removes both plugs from the jacks, restoring all apparatus to normal.

While the operator was busy completing connections between subscribers A and B, and before the calling plug of cord circuit E was inserted into the jack of Bs line, subscriber C may have initiated a call. The operator could take up this call by inserting the answering plug of cord circuit F into the jack of Us line. Relays 5 and 6 of the cord circuit F would be operated, relay 6 completing a circuit for listening relay 7. Listening relay 7 would not operate, however, for a circuit is now completed through both windings, the energizing eifect of one being neutralized by that of the other.

The circuit including the upper winding is from battery, through the upper winding of relay 7 alternate contact of supervisory relay 6 and supervisory lamp 8 to ground (cord circuit F), while the circuit including the lower winding is from battery through contact 11 of relay 7 of cord circuit E, common conductor 12, contact 10 of relay 7, contact 13 of relay 14L in cord circuit F, lower winding of the listening relay 7, alternate contact of supervisory relay 6 and supervisory lamp 8 to ground. As soon, however, as the operator completes the establishment of connection between lines A and B, relay 7 of cord circuit E will release, as hereinbefore described, thereby removing battery from one terminal of the lower winding of fice, link circuits for interconnecting the.

lines, an operators telephone set, a relay having operatlng and neutralizing windmgs associated with each link circuit operatingupon connection thereof with a calling line to include the operators telephone set in circuit therewith, and contacts on one of said relays engaged upon the operation thereof to close a break in circuit with the neutralizing winding of the relay of another link circuit preventing the operation thereof when said another link circuit is connected with another line.

2. In a telephone exchange system, subscribers lines terminating at a central ofiice, link circuits for interconnecting the lines, an operators telephone set, a relay having an operating winding and associated with each link circuit operating upon con nection thereof with a calling line to include the operators telephone set in circuit therewith, and a neutralizing winding for the relay of another link circuit whose circuit is prepared by the operation of the relay of the busy link circuit to prevent the operation of the relay of said another link circuit when connected with another line.

In witness whereof, I hereunto subscribe my name this 2 ith day of May A. D., 1916.

' LEWIS H. JOHNSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

